Gas nozzles and methods of operating the same



E. HOLLWEG April 28, 1964 GAS NOZZLES AND METHODS OF OPERATING THE SAME Original Filed Feb. 15, 1955 IN V EN TOR. 1/2 49 A WJ/JWAZ' United States Patent 3,131,054 GAS NOZZLES AND METHODS OF OPERATING THE SAME Erich Hollweg, Schmiden, Stuttgart, Germany, assignor to Siegerlander Kupferwerke G.m.b.H., Weidenau (Sieg), Germany Continuation of application Ser. No. 488,219, Feb. 15, 1955. This application Dec. 21, 1960, Ser. No. 77,353 Claims priority, application Germany Feb. 20, 1954 1 Claim. (Cl. 75-60) This invention relates to a nozzle for treating molten metal especially molten iron, with oxygen. This application is a continuation of applicants co-pending application Ser. No. 488,219, filed on February 15, 1955, now abandoned.

In a known refining process, technically pure oxygen gas is blown through a water-cooled nozzle from above to the surface of the metal bath with a pressure such that the stream of gas penetrates deeply into the bath and performs its Work of refining there. Refining processes are also known which are carried out, for example, in an electric furnace or a Siemens-Martin furnace, in which the nozzle itself dips into the liquid metal and gaseous oxygen under high pressure is applied to the melt below the surface of the bath. In both cases the small durability of the oxygen nozzle causes considerable difficulty. By cooling the nozzle with water which circulates through a chamber surrounding the nozzle, the wear on the nozzle can be reduced. Nevertheless, it is still considerable. Further, in the known water-cooled oxygen nozzles, inconvenience may occur because leaks are often not at once recognized and, during the refining, water vapor or steam is blown into the metal in an uncontrolled manner. Finally, working with the known water-cooled nozzles is difficult owing to the pipes or hose necessary for the supply and discharge of the water.

The invention is concerned with increasing the durability of the oxygen nozzles used for treating metal baths, especially iron baths, and their structural simplification. The invention proposes to depart fundamentally from the principle of water-cooling these nozzles and uses the oxygen employed for the refining as the cooling medium.

The technically pure oxygen gas used in iron and steel works which contains about 9899.5% O is stored be hind the plant which produces the oxygen in containers under a pressure of about 25 atmospheres and is adjusted on its passage to the individual places of use to the pressure required there. When refining steel, oxygen at a pressure of about 5-10 atmospheres is generally used.

According to the invention, the highly compressed oxygen gas at a greater pressure than is required for introducing the oxygen into the metal bath is first conducted into a cooling chamber which surrounds a central blast tube and is expanded there to a lower pressure, but at the most to the pressure at which it is used, and is introduced from the cooling chamber into the central blast pipe and blown onto or into the metal bath. On expanding the oxygen in the chamber surrounding the nozzle, a strong cooling eifect is produced which is used in accordance with the invention for protecting the nozzle.

The amount of the expansion and, therefore, of the cooling depends on the size of the cooling chamber surrounding the central blast pipe. Since pressure is consumed in the expansion the nozzle is operated at an oxygen pressure which exceeds by a suitable amount the pressure necessary for treating the metal bath. If higher pressures are used, the gas after leaving the cooling chamber and before its entry into the central blast pipe must be adjusted, for example by known means, to the necessary pressure at which it is used.

Two embodiments of a nozzle for refining steel in accordance with the invention are illustrated, by way of example, in the accompanying drawing, in which:

FIGS. 1 and 2 are cross-sections through the nozzles of different constructions.

Referring to FIG. 1, the nozzle consists of a central blast pipe 2 for the oxygen and a cooling chamber 3 which surrounds this pipe. The oxygen gas is supplied to the latter at a pressure which is above the pressure necessary for treating the metal bath. For this purpose the pipe 4 is used. The oxygen expands in the cooling chamber 3 to the pressure at which it is to be used and produces a considerable cooling effect. It leaves the cooling chamber by the pipe 5 which conducts it directly into the central blast pipe 2. A pressure regulator D may be arranged in the pipe 5.

In the nozzle illustrated in FIG. 2 the cooling chamber is provided with helical guide surfaces 6 which have the effect that the oxygen introduced through the pipe 4 circulates around the central blast pipe 2 and cools it while expanding.

The improvement afforded by the instant invention is obvious; all difficulties which arise in the water cooling of the nozzles are eliminated. These difiiculties are due to the danger of the nozzle leaking and to the fact that the nozzle must be moved not only with the oxygen supply pipe but also with the water pipes or hoses. The slmplification due to the elimination of the cooling water pipes is of considerable importance in operation.

The invention is not limited to nozzles for treating or refining steel baths. The inventive idea of cooling a nozzle by the expansion of gaseous oxygen can be made use of in all cases in Which nozzles are operated with oxygen or with air enriched with oxygen, for example zfllsohin blast furnace nozzles, cupola furnaces and s0 ort I claim:

The method of operating a nozzle having a central blast pipe for introducing oxygen gas containing 98 to 99.5% 0 under a pressure of about 5-10 atmospheres into molten metal to be refined and a cooling chamber surrounding the blast pipe, which comprises storing the oxygen gas in containers behind the plant which produces it, conducting the oxygen gas from said storing containers into said cooling chamber under a pressure of about 25 atmospheres and at a rate necessary for the refining process, expanding the oxygen gas in said cooling chamber to the operating pressure of said nozzle in said refining process, cooling said nozzle by the refrigerating effect thus obtained, introducing the expanded oxygen gas into said blast pipe and blowing it into the molten metal to be refined.

References Cited in the file of this patent UNITED STATES PATENTS 58,145 Sinnott et al Sept. 18, 1866 2,454,892 Sprow Nov. 30, 1948 2,598,393 Kalling et a1. May 27, 1952 2,632,302 Steele Mar. 24, 1953 FOREIGN PATENTS 16,346 Great Britain of 1887 16,726 Great Britain of 1888 

